In a large serving bowl, combine lettuce, apples, almonds, cooked bacon, and blue cheese. Set aside for a moment.
Make the challah croutons: heat oil in a medium skillet over medium-high heat. Saute challah bread in oil, stirring occasionally until croutons are golden and crispy. Season with salt and pepper to taste, cool croutons and add to salad.
Make the dressing: In a small bowl, whisk apple cider, vinegar, and mustard until smooth. Gently drizzle oil into mixture, whisking constantly until incorporated. Season dressing with salt and pepper to taste.
Right before serving, drizzle dressing over salad and toss to combine. Serve immediately. Enjoy!